[interop][SwiftToCxx] generics: support inOut generic param

Author: hyp

lib/PrintAsClang/PrintClangFunction.cpp

@@ -223,7 +223,8 @@ class CFunctionSignatureTypePrinter
                                  bool isInOutParam) {
     // FIXME: handle optionalKind.
     // FIXME: handle isInOutParam.
-    os << "const ";
+    if (!isInOutParam)
+      os << "const ";
     if (languageMode == OutputLanguageMode::Cxx) {
       // Pass a reference to a template type.
       os << genericTpt->getName();
@@ -425,7 +426,10 @@ void DeclAndTypeClangFunctionPrinter::printCxxToCFunctionParameterUse(
       // FIXME: NEED to handle boxed resilient type.
       // os << "swift::" << cxx_synthesis::getCxxImplNamespaceName() <<
       // "::getOpaquePointer(";
-      os << "reinterpret_cast<const void *>(&";
+      os << "reinterpret_cast<";
+      if (!isInOut)
+        os << "const ";
+      os << "void *>(&";
       namePrinter();
       os << ')';
       return;

test/Interop/SwiftToCxx/generics/generic-function-execution.cpp

@@ -108,5 +108,13 @@ int main() {
 // CHECK-NEXT: Bool value 1=false
 // CHECK-NEXT: other values=-78,45
   }
+
+  {
+    int x = 42;
+    int y = -13;
+    genericSwap(x, y);
+    assert(x == -13);
+    assert(y == 42);
+  }
   return 0;
 }

test/Interop/SwiftToCxx/generics/generic-function-in-cxx.swift

@@ -21,9 +21,16 @@ public func genericPrintFunctionMultiGeneric<T1, T2>(_ x: Int, _ t1: T1, _ t1p:
     print("other values=\(x),\(y)")
 }
 
+public func genericSwap<T>(_ x: inout T, _ y: inout T) {
+  let t = x
+  x = y
+  y = t
+}
+
 // CHECK: SWIFT_EXTERN void $s9Functions20genericPrintFunctionyyxlF(const void * _Nonnull x, void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericPrintFunction(_:)
 // CHECK-NEXT: SWIFT_EXTERN void $s9Functions32genericPrintFunctionMultiGenericyySi_xxSiq_tr0_lF(ptrdiff_t x, const void * _Nonnull t1, const void * _Nonnull t1p, ptrdiff_t y, const void * _Nonnull t2, void * _Nonnull , void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericPrintFunctionMultiGeneric(_:_:_:_:_:)
 // CHECK-NEXT: SWIFT_EXTERN void $s9Functions26genericPrintFunctionTwoArgyyx_SitlF(const void * _Nonnull x, ptrdiff_t y, void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericPrintFunctionTwoArg(_:_:)
+// CHECK-NEXT: SWIFT_EXTERN void $s9Functions11genericSwapyyxz_xztlF(void * _Nonnull x, void * _Nonnull y, void * _Nonnull ) SWIFT_NOEXCEPT SWIFT_CALL; // genericSwap(_:_:)
 
 // CHECK:      template<class T>
 // CHECK-NEXT: requires swift::isUsableInGenericContext<T>
@@ -44,3 +51,9 @@ public func genericPrintFunctionMultiGeneric<T1, T2>(_ x: Int, _ t1: T1, _ t1p:
 // CHECK-NEXT: inline void genericPrintFunctionTwoArg(const T & x, swift::Int y) noexcept {
 // CHECK-NEXT:   return _impl::$s9Functions26genericPrintFunctionTwoArgyyx_SitlF(reinterpret_cast<const void *>(&x), y, swift::getTypeMetadata<T>());
 // CHECK-NEXT: }
+
+// CHECK:      template<class T>
+// CHECK-NEXT: requires swift::isUsableInGenericContext<T>
+// CHECK-NEXT: inline void genericSwap(T & x, T & y) noexcept {
+// CHECK-NEXT:   return _impl::$s9Functions11genericSwapyyxz_xztlF(reinterpret_cast<void *>(&x), reinterpret_cast<void *>(&y), swift::getTypeMetadata<T>());
+// CHECK-NEXT: }